Incremental Value of Inefficient Deformation Indices for Predicting Response to Cardiac Resynchronization Therapy

Abstract

Previous studies have identified four clinical characteristics associated with a favorable response to cardiac resynchronization therapy (CRT): female gender, left bundle branch block (LBBB), QRS duration ≥ 150 msec, and nonischemic etiology of heart failure. The aim of this study was to evaluate the incremental value of baseline inefficient deformation and time delay indices over clinical characteristics for predicting CRT response. Speckle-tracking longitudinal strain was analyzed in 119 CRT candidates. Patients were divided into subgroups according to sex (male vs. female), QRS morphology (LBBB vs. non-LBBB), QRS duration (≥150 vs. <150 msec), and heart failure etiology (ischemic vs nonischemic). Inefficient deformation was indexed by the septal systolic stretching that occurred after prematurely terminated shortening (systolic rebound stretch in the septal wall) and the absolute differences between peak strain and end-systolic strain across 16 segments (strain delay index). Time to peak strain was measured to derive the septal-to-lateral delay and the 12-segment standard deviation of time to peak strain. CRT response was defined as 6-month end-systolic volume reduction ≥ 15%. Patients with one of the four favorable characteristics were more likely to exhibit other favorable characteristics and had greater amounts of inefficient deformation than those without. In contrast, time delay indices were not significantly different in any pairwise comparison except for that between patients with and those without LBBB. Of the 43 patients for whom 6-month follow-up data were available, CRT response was found in 26 (60%). Systolic rebound stretch in the septal wall and strain delay index rather than time delay indices provided significant incremental value over clinical characteristics when predicting CRT response. Combined systolic rebound stretch in the septal wall (or strain delay index) and favorable characteristics may help identify CRT responders.